In 2010, the China Environmental Protection Foundation and Jody Xiong of DDB China created a visual campaign to encourage commuters to walk instead of drive. They achieved this by placing a giant bare tree on white canvas in an intersection and green washable paint on both sides of the crosswalk. The more green foot prints left, the more the tree blooms! The murals were then hung as billboards in different parts of the city.

I would love to see this come back, not only in China, but in other heavy populated cities that suffer from high amounts of car pollution.